Adam: Tektronix function generators often have slider switches
on the back to operate at 100V, 120V, 220V, or 240 V. Students
can "inadvertently" shift those, and then all the voltage readings
are wrong because the line base is wrong. I've seen this a problem
there, and with other devices that accept multiple source voltages.

Don't have the same DMM you have, but I've got a BK unit that has
the same input voltage selection potential (pun unintended) problem!